Complex physical properties of EuMgSi – a complementary study by neutron powder diffraction and¹⁵¹Eu Mössbauer spectroscopy

Abstract

International audienceX-ray pure samples of EuMgSi were synthesized by reactions of the elements in sealed niobium tubes using a high frequency and subsequently a resistance furnace. The structure was investigated by single crystal X-ray diffraction: TiNiSi-type, Pnma, a = 769.5(2), b = 455.0(1), c = 836.9(2) pm, wR2 = 0.033 [I ≥ 2σ(I)], and 705 F2 values with 20 variables. Powder synchrotron radiation diffraction experiments did not reveal any structural changes down to 4.3 K. Magnetic susceptibility data and 151Eu Mössbauer spectra clearly indicate a stable Eu2+ configuration. Two distinct magnetic anomalies around 12 and 14 K can be observed for different samples with dc- and ac-susceptibility, heat capacity and resistivity measurements. Fitting of hyperfine field splitting as a function of temperature (151Eu Mössbauer spectroscopy data) with a Brillouin function also leads to a magnetic ordering around 14 K. Electronic structure calculations in coincidence with the resistivity measurement prove narrow (or nearly zero) gap-semiconducting behaviour. The calculated band gap energy of 0.03 eV should be considered with precautions due to the accuracy of this method. An incommensurate magnetic structure with the propagation vector k = [qx ≈ 0.37, 0, 0] was determined using neutron diffraction data at 5.5 K. In consensus of dc- and ac-susceptibility and neutron powder diffraction a complex combination of antiferromagnetic and ferromagnetic interactions, most likely by super-exchange, is confirmed. These cause two magnetic ordering temperatures, though only one independent crystallographic Eu site in terms of the crystal structure is present in EuMgS

The Solid Solution Eu1–xSrxAuIn

“…The EuMgSi magnetic structure was also investigated by neutron powder diffraction (large‐area flat‐plate technique) between the two magnetic ordering temperatures and an incommensurate magnetic structure with the propagation vector k = [ q x = 0.37, 0, 0] was found. [ 50 ] A similar complex situation most likely occurs for the Eu 1–x Sr x AuIn samples presented herein; however, only a precise neutron diffraction study will provide deeper insight.…”

“…A similar situation has been observed for the isotypic Zintl phases EuMg X ( X = Si, Ge, Sn). [ 48–50 ] These tetrelides show a complex interplay of antiferromagnetic and ferromagnetic interactions. The EuMgSi magnetic structure was also investigated by neutron powder diffraction (large‐area flat‐plate technique) between the two magnetic ordering temperatures and an incommensurate magnetic structure with the propagation vector k = [ q x = 0.37, 0, 0] was found.…”

EuPtSn2 – A Stannide with Sn2 Dumbbells in a Three‐dimensional [PtSn2]2– Polyanion

“…Such fields are usually observed for ternary europium stannides . Most part of the europium atoms, however, show still incomplete hyperfine field splitting at 5.5 K. The most likely complex magnetic structure can only be determined by neutron diffraction using the large‐area flat‐plate geometry technique, as successfully applied for the magnetic structures of EuPdSn and EuMgSi …”

“…The 119 Sn Mössbauer spectra at 5.5 and 78 K are depicted in Figure . They show a single component at an isomer shift of around 2 mm · s –1 typical for tin in intermetallic compounds . Both spectra were fitted using three signals each belonging to one of the crystallographically independent tin sites in a fixed 1:1:2 ratio (Wyckoff sites 8 f and 2 × 4 c ).…”

Synthesis, Crystal Structure, Polymorphism, and Magnetism of Eu(CN3H4)2 and First Evidence of EuC(NH)3

“…Within the recent decades, several technological innovations disrupted the rare-earth market [2], in turn stimulating the scientific quest for future materials. One vibrant field is the study of Eu 2+ compounds whose complex crystal structures are coupled with application-relevant properties including, to name only some recent examples, luminescence [3][4][5][6], field-induced reversal of the magnetoresistive effect [7], and complex magnetism [8,9]. The most renowned magnetic compounds are the europium chalcogenides that are considered ideal 3D Heisenberg systems [10].…”